You can't withdraw bonus bets or bet credits, but you can withdraw winnings. Bet credits and bonus bets cannot be withdrawn, but they can be used to wager on other sporting markets your sportsbook has to offer. Some sportsbooks make you use your bonus funds or bet credits in one lump sum.
With both sign-up bonuses and betting promotions, if the bonus bet is successful, the bookmaker will only return the winnings from that wager, not the betting stake.