A Birthday Sandwich is a sexual innuendo for a man laying on his back, a woman straddling him, and another man filling the final hole of said woman. Said sandwich must be received on birthday.
A BirthdaySandwich on any other occasion would be commonly known as a Three-Way.
1) Bitch who believes the "pleasure" of giving her gifts is its own reward and never gives a grain of respect in return.
2) Bitch who accepts gifts from people she does not like.
For this reason above, friends regardless of gender should never make any gifts for each other in any form including such simple as tickets for beer. The exception to this rule is for families and engaged couples. Thanks to this rule you avoid a birthday whore 99% of time.