The Boom Boost is a feature for Sonic Dash 2: Sonic Boom. When used, it grants several in-game bonuses.
When winning a Boom Boost from a Prize (mostly obtained via Missions or Events), the player gets an hour added to its total duration time. The first Boom Boost will last one hour; after the player uses it up and then collects another one, it will last two hours; the next will last three hours etc. If the player does not let the Boom Boost run out, the next one will only add an hour to the total time the current Boom Boost is supposed to last.
A duration of a Boom Boost for a week can be purchased for $1.99. Doing so also disables most in-game ads (other than those offered to gain an additional free revive during each run).