Once! It was probably the most miserable day of my life, but in retrospect it's just a totally awesome story. I've gotten sicker from street food elsewhere (giardia in the amazon was insanely uncool), but this was particularly crazy.
I was traveling from Varanasi (India) to Kathmandu (Nepal); you can fly, but I decided to see some scenery and do it by train and bus. I left Varanasi on the day before Holi, which is the indian holiday where hooligan kids throw dried paint at people who don't look like they want to be hit with lots of dried paint. I got to Gorakhpur at like 1:30am on the train, had a shitty hostel booked and aimed to catch the notoriously small government bus to the border town at 7am the next day. Got myself some samosas from a random street vendor since I hadn't eaten for like eight hours, devoured them, and went to sleep. Woke up at around 5am with my stomach churning; promptly threw up a bunch, but had to get packing and go find the bus. First thing when I walk outside? Paint in the face. A lot of laughing kids. More paint. People saying "why are you traveling on Holi? Very bad idea!" or even worse: "why are you playing holi? just tell them no!" (as if that worked for me even once).
Once I found the bus, it took me about twenty minutes of bumpy riding before I had to throw up again. Luckily I'd gotten the rear-most window seat, so I just leaned over and vomited out the window. It was terrible, but it worked. I think I made the poor woman with a daughter sitting next to me really, really uncomfotable, but hopefully she understood that this sick white dude covered in paint was having even less fun than she was.
But it got worse: because it was holi, kids were pelting the bus with paint pretty much the whole way to the border, so we couldn't keep the windows open on the cramped government bus with no AC. So everyone's overheating like crazy. On top of that, all out luggage is on top of the bus, and every time we have to stop (or even just slow, really), kids are climbing onto the the top of the bus, riding, and throwing more paint around, so I'm getting really paranoid about whether my frame pack is even going to be there when we finally stop.
At the border I made another stupid decision. I needed some fresh air really, really badly, so I decided to walk the 0.75 mile of no-man's land between the bus stop and the nepal visa office. Whoops. Turns out the guards literally don't give a shit about indian kids crossing the border in order to follow tourists and keep throwing paint at them. So by the time I get to the other side, the nepali guys are all just laughing at me because I am totally covered with paint and still have 8 hours of bus ride to go.
But the ride got better from there, and now it's a fun story. Plus the blanket I got in goa that I took all across india with me has some nicely set colors to it that remind me of my cool trip.
But did you ever get sick from the street food? :) I'm not that adventurous I guess.