sbuild-update: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/sbuild-update - from package: sbuild

You may install the required package with command apt-get install {package}

Error in other languages:
sbuild-update: bevel nie gevind nie
sbuild-update: comandă negăsită
sbuild-update: comando não encontrado
sbuild-update: commande introuvable
sbuild-update: command not found
sbuild-update: käsku ei ole
sbuild-update: không tìm thấy lệnh
sbuild-update: komanda nerasta
sbuild-update: Kommando nicht gefunden.
sbuild-update: kommandot finns inte
sbuild-update: komut yok
sbuild-update: nie znaleziono polecenia
sbuild-update: níor aimsíodh an t-ordú
sbuild-update: no se encontró la orden
sbuild-update: no s'ha trobat l'ordre
sbuild-update: opdracht niet gevonden
sbuild-update: parancs nem található
sbuild-update: perintah tidak ditemukan
sbuild-update: príkaz nenájdený
sbuild-update: příkaz nenalezen
sbuild-update: команда не найдена
sbuild-update: командата не е открита
sbuild-update: 命令找不到
sbuild-update: コマンドが見つかりません