sbuild-upgrade: 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-upgrade - from package: sbuild

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

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