Ted: Anyway, this is serious. I know Lily and Marshall. All the tell tale signs are here. Like this
Robin: A water bottle.
Barney: Don't touch the evidence. [to Ted] I got your back partner.
Ted: It's not just any water bottle. Notice the label is peeled off.
Ted: [v.o.] Lily always peels labels off the bottle when she's feeling guilty. This lab is not only peel off but torn up. Oh man, she must have done something bad. Which means Marshall must have been really angry, and when Marshall gets realy angry, he eats.