Because you can remove aligners easily, there are no restrictions as to what you can eat or drink. The only notable exception would be gum, which you should not chew with aligners in as they will stick to the surface.
As per general dental hygiene guidelines, smoking is also discouraged as it may cause the aligners (and your teeth!) to become discolored. Drinking alcohol in moderation is fine, as long as you understand that this and many soft drinks and juices have high sugar content and you should take extra care to clean your teeth after consuming these beverages.
You should always take out the aligners when youre eating or about to clean your teeth.
Tim Silegy, DDS