After checking many yoga studios' websites and taking an informal poll of local yogis, the general rule of thumb is to eat something light that is easily digested 2 hours before your yoga practice. The goal is to practice yoga on an empty stomach so that nothing tries to come back up during your downward facing dog!
Fruits (low acid) or veggies, yogurt, a bowl of cereal, or a granola bar are all good choices. The most important thing is to not eat anything heavy, such as meat, pasta, fried foods, or processed grains. The one exception to this is if you have low blood sugar, and then you should try to get a little bite to eat within 30 minutes of class.
What if you’re going to yoga after work and you’re starving? The best choice in this situation would be a bowl of cereal, a granola bar, or a sports bar. Still try to shoot for that 2 hour time frame, eating before you leave work if you can.
In a pinch, go with a handful of nuts or an apple on the way to class, which shouldn’t bother your stomach once your practice begins.
Ultimately, everyone is different, so try out different kinds of snacks and different time frames to see what works best for you!