When you're sleepy, try drinking coffee to refresh yourself.
Literal
Sleepy time [topic-は] coffee [object-を] drink [and] mood-change do try-[ごらん].
気分転換 = 'mood change, refreshing one's mood.' ごらん is a gentle imperative suffix (from the honorific ご覧 'honorable look'), used for soft suggestions. Combined with ~てみる (try doing) gives a kind, nudging tone. Kindly advice.